1. Field of the Invention
The present invention relates to a methods for treatment of infections of Schistosoma such as Schistosoma mansoni, Schistosoma haematobium, Schistosoma mekongi, Schistosoma japonicum, and Schistosoma intercalatum, Fasciola such as Fasciola hepatica and Fasciola gigantica, Fasciolopsis buski, Dicrocoelium dendriticum, Heterophyes heterophyes, and Metagonimus yokogawa, the method comprising administration of a pharmaceutical composition containing as active agent a compound selected from the group consisting of a desacetyl-nitazoxanide and nitazoxanide.
2. Description of the Related Art
Many parasitic infections prevalent in humans are difficult to treat. Schistosoma mansoni, the blood fluke, is the causative agent of Schistosomiasis (Bilharziosis, Bilharziose), the second most important tropical parasitic disease of man (after Malaria), and the most important trematode infection of man. Schistosoma haematobium is another important species infecting man. Over 200 million individuals suffer from schistosomiasis world wide, including several hundred thousand people in the United States. The disease is spreading due to technological advances and irrigation programs in underdeveloped countries. Humans are actively invaded by the waterliving cercariae of the parasite, which are emitted from water snails. The snails are actively invaded by miracidia, which originate from eggs, released from the human hosts into water. Pathology associated with infection is not caused by direct activity of the parasite, but rather by immunological and inflammatory responses of the host. There is no treatment for dermatitis or Katayame syndrome associated with infection, but praziquantel is reportedly effective against schistosomes.
Fasciola hepatica, the common liver fluke, is primarily a disease of sheep. However, humans are an accidental host acquiring infectious metacercariae through consumption of contaminated water, aquatic grasses or watercress. In the United States Fasciola hepatica is enzootic in extensive areas in the southern, southeastern, southwest, west and north central United States. The adult worms live in the bile ducts and release their eggs into the lumen of the intestine, which are then evacuated with feces. When eggs get into water the ciliated miracidia hatch and find a suitable intermediate host snail. After successful penetration of the intermediate host they develop through sporocyst and redial stages to cercariae which are shed from the snail. The free-swimming larvae attach themselves to firm surfaces like grass blades and form encysted metacercariae which are infective for several months under favorable circumstances. When shallow fresh water vegetation is ingested by the final host, the metacercariae excyst in the small intestine, migrate through the gut wall, cross the peritoneum and penetrate the liver capsule. After tunneling through the parenchyma for several weeks the young flukes migrate to the bile ducts and occasionally to the gall bladder and become mature. The parasite manages to survive in the presence of a vigorous host immune response. Symptoms associated with migration include epigastric pain, abdominal tenderness, urticaria and high-level eosinophilia. Bithionol has been suggested for treatment, but is not approved for use in the United States.